H. P. Friedrichs (AC7ZL) Homepage

My Books

The Voice Of The Crystal

Gallery

Here, you can take a look at images associated with the projects
appearing in The Voice of the Crystal.

This is an example of a so-called "basket" or
"basket-weave" coil. The wire comprising the coil is
wound in this fashion in order to reduce distributed
capacitance

.

This instrument, called a "boom" detector, is featured in
the book. It's comprised of various pieces of brass,
including a gas fitting from which the crystal cup is
fashioned. The crystal semiconductor material, in this
case, is iron pyrite.

This is a picture of a small collection of tuning coils,
including one wound on a glass jar, along with the
spools of enameled magnet wire from which the coils
are fashioned.

These are fixed condensers (capacitors) fashioned
using techniques discussed in The Voice Of The
Crystal. Electrode materials include both copper and
aluminum foils, while dielectrics include wax paper and
various plastic films. Condenser rolls are potted into
cardboard housings with bee's wax.

This image shows some of the internal detail of the
fixed condensers described above.

I call this instrument a "crank coil." To be precise, it's a
double-tapped adjustable tuning inductance, which
utilizes a novel arrangement of screw threads to allow
precise positioning of the coil taps. Construction details
for this coil appear in the book.

This, believe it or not, this is the driver for a set of home
made headphones. To use it, the earpieces from a
medical stethoscope are connected to the open tube
which projects from the front of the instrument. It's quite
sensitive.

This is another type of headphone described in The
Voice Of The Crystal. This headphone is novel,
because it's operation depends upon the movement of
a piezoelectric crystal which was harvested from an old
electronic cigarette lighter.

Headphones are one of those parts that "experts" tell
you can't be fabricated at home using hand tools. Well,
here's yet another headphone design using scrap
magnets and coils of wire wound upon cardboard
spools. The floor of a mushroom can is utilized as a
diaphragm. The rear cover of the instrument is a
die-cast fence post cap.

Here's another example of a radio component that
"can't" be build at home, yet The Voice Of The Crystal
shows you how. This is a very nice variable condenser
(capacitor) used as part of a radio's tuning circuitry. The
condenser blades are made from sheet aluminum,
separated by an acetate dielectric.